1. Field of the Invention
The present invention provides an improved shear band for use in non-pneumatic tires, pneumatic tires, and other technologies. The improved shear band is uniquely constructed of honeycomb shaped units that can replace the elastomeric continuum materials such as natural or synthetic rubber or polyurethane that are typically used. In particular, honeycomb structures made of high modulus materials such as metals or polycarbonates are used that provide the desired shear strains and shear modulus when subjected to stress. When used in tire construction, improvements in rolling resistance can be obtained because of less mass being deformed and reduced hysteresis provided by these materials. The resulting mass of the shear band is greatly reduced if using low density materials. Higher density materials can be used (such as metals) without increasing mass while utilizing their characteristic low energy loss.
2. Description of the Related Art
Those skilled in the art of pneumatic tires have developed a wealth of experience in adapting the tire construction to achieve a variety of performance combinations for tread wear, handling, wet and dry traction, rolling resistance, etc. As an example of this adaptation, a pneumatic or non-pneumatic tire may be optimized for low weight and low hysteresis which results in improved rolling resistance and improved fuel economy. For example, tire designers frequently try to minimize the weight and hysteresis of the materials that constitute the tire.
Non-pneumatic or structurally supported tires have been disclosed in the art. For example, U.S. Pat. No. 6,769,465, commonly owned by the applicant of the present invention, relates to a structurally supported resilient tire that supports a load without internal air pressure. The content of this patent is hereby incorporated by reference in its entirety. In an exemplary embodiment, this non-pneumatic tire includes a ground contacting portion and side wall portions that extend radially inward from the tread portion and anchor in bead portions that are adapted to remain secure to a wheel during rolling of the tire. A reinforced annular band is disposed radially inward of the tread portion. This shear band includes at least one shear layer, a first membrane adhered to the radially inward extent of the shear layer and a second membrane adhered to the radially outward extent of the shear layer. The invention of U.S. Pat. No. 6,769,465 provides several advantages including, for example, the ability to operate with partial or no inflation pressure and the flexibility to adjust the vertical stiffness of the tire somewhat independently of the ground contact pressure. This invention also provides a relatively well equilibrated contact pressure throughout the contact area.
By way of further example, U.S. Pat. No. 7,201,194, commonly owned by the applicant of the present invention, also relates to a non-pneumatic tire. The content of this patent is also hereby incorporated by reference in its entirety. In an exemplary embodiment, this non-pneumatic tire includes an outer annular shear band and a plurality of web spokes that extend transversely across and radially inward from the annular band and are anchored in a wheel or hub. In certain exemplary embodiments, the annular shear band may further comprise a shear layer, at least a first membrane adhered to the radially inward extent of the shear layer and at least a second membrane adhered to the radially outward extent of the shear layer. In addition to the ability to operate without a required inflation pressure, the invention of U.S. Pat. No. 7,201,194 also provides advantages that include a more uniform ground contact pressure throughout the length of the contact area.
As described for the exemplary embodiments of the references discussed above, both used an annular shear band comprising a shear layer to provide desirable performance benefits in a tire. The shear layer described by these references is composed of an elastomeric material such as natural or synthetic rubber or polyurethane. However, these materials have proven to create more hysteresis and add more weight than desirable which results in a tire having a higher rolling resistance. Accordingly, there is a need for an improved shear layer construction that satisfies the aforementioned need without compromising the shear modulus and shear strains needed in the shear layer in order for the tire to work as intended. As described below, Applicants have discovered an advantageous construction for the shear layer that provides lower weight and hysteresis without compromising other properties that are needed from the shear layer. This improved construction for the shear layer has application in pneumatic tires, non-pneumatic tires, hybrid tires that operate at reduced inflation pressure in conjunction with structural support form an annular band, and other products as well.